Two-piece metal containers (e.g., beverage cans made of steel or aluminum) generally comprise an integral body wall and a container side wall having an end attached to the side wall to form the finished container. In forming such containers, a circular blank of metal stock is first deformed into a shallow cup. These cups are placed within a vertical chute (with their open ends facing sideways) and sequentially gravity fed through the chute bottom onto a positioning device where they are contacted by a horizontally extending reciprocating piston for transfer to a location in alignment with the punch.
The drawing and ironing press generally comprises a tool pack having an opening in alignment with a plurality of axially spaced forming rings therewithin. The punch is located on the front end of the reciprocating ram and cooperates with the rings to deform the cup into a container having the bottom wall of a particular configuration and a generally cylindrical side wall. The punch is typically driven with a crank and in the forward stroke the punch engages the inside surface of the cup bottom wall (positioned by the cupfeeder into alignment with the tool pack opening) with the side wall extending along the punch sides. Continued movement of the punch in its forward forming stroke causes the cup side wall to be stretched by the rings. The process is completed when the working end of the punch and cup exit the tool pack where the cup is removed by known means. The punch then withdraws through the tool pack and rearwardly of the alignment opening to enable the next in-line cup to be transferred to the opening via the piston and cylinder arrangement.
A known sensor is positioned outside the tool pack to determine whether a formed can has exited the tool pack with the punch. The absence of the can on the punch indicates that a tear-off or jam has occurred within the tool pack. The sensor triggers shutdown of the press and punch as well as disruption of the piston and cylinder assembly in its cupfeeding operation. However, the press punch and the cupfeed piston will typically require from one to three strokes to come to a complete halt and, on each of these strokes, an additional cup is fed into the tooling which creates a larger jam that may damage the tooling. Such tooling damage occurs when more than one thickness of metal is formed by the dies. Also, multiple cup jams will typically require the machine operator to place his hands in the tooling to remove the broken metal pieces, increasing the likelihood of operator injury.
It is accordingly one object of the present invention to provide a drawing and ironing press or machine with a positive cupfeeder mechanism which is capable of high speed and reliable operation with rapid shutdown in the event of jamming.
Another object of the invention is to provide a cupfeeder mechanism having a cup engaging push rod which is capable of retracting at any point in its reciprocating stroke in response to sensing of a jam within the drawing and ironing machine.
Still another object of the invention is to provide a retractable cupfeeder that also prevents further cups in the cup chute from dropping to a supply location in the transfer path to further minimize the likelihood of additional cups entering the tooling.
Yet another object is to provide yet further means entering the transfer path to prevent a cup in the supply location at the time the jam occurs from inadvertently or positively moving to the feed location (opening) in alignment with the tool pack.
Still another object is to provide a retractable cupfeeder having preselected low mass components so that the inertia of the retracting push rod components is small and its strength and rigidity high so as to enable instantaneous (e.g., 30 milliseconds at 500 cans per minute) retraction to occur during high speed normal running operation.